Mass-Spectra of Annelated 4H-3,1-Oxazin-4-ones

Abstract

Electron-impact fragmentation of 2-R-4H-3,1-benzoxazin-4-ones involves primary losses of CO₂ and R; there is also loss of ketene when R is methyl. The ion RCO⁺ is a major daughter. Successive losses of CO₂and RCN yield an ion m/z 76 formulated as dehydrobenzene radical cation. In the case of 2-methyl-4H-3,1-naphth[2,3-d]oxazin-4-one, the 2,3-dehydronaphthalene ion is produced efficiently, and linked scans (B/E) were used to demonstrate that it loses C₄H₂ ( diacetylene ) in a retro Diels-Alder reaction.